1. Field of the Invention
The invention relates to a flaw detection testing device for a hub unit that supports a wheel of an automobile.
2. Description of Related Art
There is known a hub unit that includes a hub wheel, an inner ring member and rolling elements and that rotatably supports a wheel of an automobile (for example, see Japanese Patent Application Publication No. 2007-276780 (JP-A-2007-276780)). The hub wheel has a hub spindle. The inner ring member is fixed to the vehicle body-side end portion of the hub spindle. The rolling elements are rollably provided between an inner ring raceway and an outer ring raceway. The inner ring raceway is formed on the outer periphery of the hub spindle and inner ring member. The outer ring raceway is formed on the inner periphery of an outer ring.
A small-diameter portion is formed at the vehicle body-side end portion of the hub spindle via a step in the hub unit. The inner ring member is fitted around the outer peripheral surface of the small-diameter portion. The inner ring member is fixed to the hub spindle by clinching, by plastically deforming the distal end of the small-diameter portion, protruding from the inner ring member, radially outward.
The rotational driving force of a drive shaft is transmitted to the hub unit via a constant velocity joint. There is known the following manner of transmitting the rotational driving force. Spline teeth are formed at the distal end portion of the small-diameter portion of the hub spindle, that is, the axial end surface of the clinched portion, spline teeth are also formed on the axial end surface of the outer ring of the constant velocity joint, facing the axial end surface of the clinched portion, and both the spline teeth are in mesh with each other (for example, see Japanese Patent Application Publication No. 2008-174178 (JP-A-2008-174178)).
The above-described hub unit is subjected to flaw detection test to check whether a flaw or a crack has occurred in the clinched portion. This test is carried out, for example, in the following manner. The hub unit is rotated in a state where an eddy current sensor is brought close to the clinched portion with a set clearance left, and then a change in the value detected by the eddy current sensor is acquired. In the case of the hub unit described in JP-A-2007-276780, a flaw detection sensor is brought close to the axial end surface of the clinched portion to thereby make it possible to carry out a flaw detection test. On the other hand, in the case of the hub unit described in JP-A-2008-174178, the spline teeth are formed on the axial end surface of the clinched portion, and a flaw, or the like, tends to occur near the intersection between the spline teeth and the outer peripheral surface of the clinched portion. Therefore, it is necessary to carry out the test with the flaw detection sensor brought close to the outer peripheral surface. However, the shape of the outer peripheral surface of the clinched portion is not restrained when the clinched portion is plastically deformed. Therefore, the outside diameter size tends to vary from product to product, and it is necessary to adjust the clearance between the outer peripheral surface of the clinched portion and the eddy current sensor for each product in order to carry out an accurate flaw detection test.